1. Field of the Invention
The present invention relates to a solid-state sensor for determining the concentration of gas species, in particular oxygen, which can react with hydrogen, which solid-stage sensor can also operate at room temperature.
2. Discussion of the Background
The determination of the oxygen content in a gas mixture or in liquids is an important problem from the industrial, biological, environmental, and still other, view points.
Very often, continuous monitoring is required, as in rivers, lakes or seas, to keep controlled the level of pollution caused by organic materials. Such a requirement can also occur in the case of biological liquids in general, or in gases generated by combustion processes, and other processes.
For that purpose, a method of voltametric type (Clark's method) is used [see: M. Kleitz, A. Pelloux, M. Gauthier in "Fast Ion Transport in Solids", page 69, Elsevier North Holland, Inc. (1979)].
During the past ten years, potentiometric systems were also introduced, which use a solid conductor for O.sub.2, usually zirconium oxide doped with yttrium, which operate successfully only at temperatures higher than 400.degree.-500.degree. C. [see: E. Siebert, J. Fouletier, S. Vilminot "Solid State Ionics," 9 and 10 (1983) 1291].
Recently, attempts were carried out aiming at lowering the operating temperature of the potentiometric sensors, by studying other types of solid electrolytes [see: N. Miura, J. Hisamoto, S. Kuwata, N. Yamazoe "Chemistry Letters" (1987) 1477; T. Inoue, K. Eguchi, H. Arai "Chemistry Letters" (1988) 1939; S. Kuwata, N. Miura, Y. Yamazoe "Chemistry Letters" (1988) 1197].